Industrial x-ray systems have long been used in a number of fields, including NDT. Typically, they comprise several units: a tubehead that includes an x-ray tube, a cooling arrangement to remove heat from the x-ray tube, a source of electrical power, and a control unit. The x-ray tube typically includes a target that generates x-rays when bombarded with an electron beam accelerated between a cathode and an anode. The anode can be the target itself, or another material interposed between the anode and the cathode can be the target. (“Anode” here includes both an anode serving as the target and the combination of separate target material and the anode.) The anode gets heated in the process of generating x-rays, and typically needs to be cooled for practical operation.
One common type of cooling is gas cooling. Typically, a finned heat sink is thermally coupled with the anode and is cooled with gas such as air blown through the fins with a high capacity muffin fan. The gas cooling unit is affixed at the anode end of the tubehead. Another common type of cooling is liquid cooling. A fitting with an internal conduit is thermally coupled with the anode and liquid from an outside source is circulated through the fitting. In some cases, air cooling is preferable, as it does not require an outside source of liquid and a pump and thus fewer components need to be moved and set up. In other cases, liquid cooling is preferable, for example when operating the x-ray systems in volatile gas environments where there is a danger from possible sparking at the fan motor. In such environments, the outside source of liquid coolant and the pump can be spaced from the tubehead such that they are outside the volatile gas environment.
LORAD of Danbury Conn., a division of Hologic, Inc. of Bedford, Mass., has been selling x-ray systems for a number of years in this country with gas cooling as well as x-ray systems with liquid cooling. A number of other companies also have offered system with one type of cooling of the other type. For example, LORAD currently offers gas cooled tubeheads and also liquid cooled tubeheads under the commercial designation LORAD LPX series. However, to the inventors' knowledge, x-ray tubeheads that can be conveniently configured in the field to use either type of cooling have not been commercially available.
The inventors believe that it would be desirable to provide a tubehead that can be easily configured in the field to be either liquid cooled or air cooled. For example, when it is not known ahead of time in what environment a tubehead will have to operate, currently a user may need to stock, or take on a trip, both a gas cooled x-ray system and a liquid cooling system. The inventors believe that cost savings and convenience can be achieved by providing a single tubehead that can operate with either type of cooling and is easily configured in the field to change from one type of cooling to another.